Project Leader: Dr Ignazio Maria Viola
Sponsors: Various industrial partners
Partners: Yacht Research Unit, the University of Auckland, New Zealand; Fluid Mechanics, Energy Institut de Recherche de l'Ecole Navale, Brest, France
The project aims to investigate the fluid dynamic performance of sails, which are used by modern racing sailing yachts, with the aim of understanding the specific flow features that allow modern sails to be more efficient than the wings and blades commonly used in other fields such as aeronautics.
Sail technology has grown significantly in the last 20 years allowing very high fluid dynamic performance. Most of the research on sails is performed for the America’s Cup (AC) competition, which occurs every three to four years, during which the yachts are designed, built, tested and optimised. Under the America’s Cup Class Rule, which was used from 1992 to 2007, very efficient sails were developed. In particular, the maximum lift coefficient and the maximum lift/drag ratio can be used to judge the performance of a wing, considering that these indices will increase with higher aspect ratios. These AC sails can generate maximum lift coefficients higher than 3.5, levels that are normally achieved only by thicker aerofoils with multiple slotted flaps. Moreover these sails develop lift/drag ratios higher than 13 and have aspect ratios between 1 and 1.5, while such lift/drag ratios are normally only achieved by wings with aspect ratios of at least 5.5. Therefore, the recent developments in sail aerodynamics allowed achieving very efficient aerodynamic wings. However, because sails have been investigated significantly less than other conventional wings used in industrial applications, such as airplane wings, the fluid dynamic features, which make sails so efficient, are still widely unknown.
Understanding these aerodynamics feature will allow enhancing further the performance of sails and, very importantly, will allow the cross fertilisation towards different fields of applications where thin and high-lift airfoils are used.
Dr Ignazio Maria Viola
Lecturer in Naval Architecture